Not Applicable.
The present invention relates to automated sheet feeder apparatus for scanning equipment and the like, and more particularly to a configuration that facilitates document separation and spacing for use with universal document feeder apparatus associated with high-speed image scanning equipment requiring a high-volume document throughput.
Automated high-speed image scanning equipment utilizes an imaging device to scan the images from an input or source document. Such equipment must feed and transport documents to the imaging device quickly, smoothly, and automatically, and must be trouble-free. The feeding equipment must quickly and smoothly feed each original document or individual sheet from the backlog queue of input or source documents waiting to be scanned to the transport apparatus. The transport apparatus then brings each document or sheet to the imaging device. To achieve high-volume throughput, the high-volume feeder apparatus must be able to supply the individual documents or sheets in a spaced relationship to the input section of the transport apparatus in a manner that is completely reliable and trouble-free.
A problem associated with high-speed image scanning equipment found in the prior art is that the individual source or input documents commonly are not standardized. They vary in shape and size, and come in a variety of different thicknesses (e.g., sheets ranging from an onionskin thickness to thick card stock). This mandates that each non-uniform document be processed or handled in a uniform manner.
Another related problem is that, in the majority of instances, the input or source document is an original document or a document that is not easily replaced. It becomes imperative that the document feed mechanism not damage any of the source documents under any circumstances.
A persistent problem found in the prior art is the more or less random feeding of multiple documents at one time by the document feed mechanism, rather than a single sheet. The problem is commonly referred to, by those skilled in the art, as the xe2x80x9cmulti-feedsxe2x80x9d problem. The multi-feeds problem is made even more critical when a high-volume document throughput is required for high-speed image scanning equipment and the like. In such situations, the individual source documents waiting to be scanned are in a stack, and either the top or bottom document is fed sequentially to the image scanner by the document feed mechanism.
Several factors have been blamed for this negative result. One such factor is the weight of the skimmer roller assembly (which rests on top of the first document in the stack of documents waiting to be scanned). Another such factor is the underlying dynamics of the friction that the bottom and top sheets experience as the document feed mechanism accelerates the next sheet from the stack forward. Yet another such factor is the spacing required between individual documents as documents enter the document feed mechanism and are sequentially processed.
Yet another common problem with certain document feed mechanisms for high-speed image scanning equipment and the like found in the prior art is that, over time, this equipment will occasionally cause bottlenecks and/or jam-ups of downstream equipment, having an obvious negative effect on overall document throughput. Sometimes the problem can be corrected by timely maintenance of the document feed mechanism. High-speed image scanning equipment that provides for high-volume document throughput necessitates a reliable document feed mechanism that is easy to maintain and is capable of fulfilling document throughput requirements.
A particular prior device currently in use employs a relatively narrow skimmer roller at the entrance to the feeder together with an adjustable separate weight that helps the skimmer roller to grip the paper. The prior device also uses a pair of counter-rotating shafts with interleaved roller portions that are designed to advance the top page while separating any adjacent or lower pages. The counter-rotating shafts are set an adjustable distance apart. The inventors have found that this arrangement results in paper jams and multifeeds when stacks of documents with different thicknesses are introduced. Finally, in that device there is space between the skimmer roller and the interleaved forwarding and separator rollers. Sheets being fed sometimes buckle or bunch up in that space.
Another prior device currently in use utilizes a driven infeed roller nipped with a separator roller coupled by a drag and recoil mechanism to a fixed shaft. The infeed roller urges one face of the sheet forward, while the separator roller acts as a drag on the opposite face of the sheet. If multiple sheets pass between the advancing and the separator rollers, the infeed roller will urge the first sheet forward and the separator roller will drag on the other sheet. Since the friction between the separator roller and the sheet is higher than the friction between two sheets, the separator roller will prevent the passing of the lower sheet. While this is not a xe2x80x9creversingxe2x80x9d roller per se, but rather a simple xe2x80x9cdragxe2x80x9d on the lower of two adjacent sheets, it tends to separate the two while the upper sheet passes through the gap under the drive of the infeed roller.
Also in the prior art are various arrangements for the separator roller. The first of these is an earlier development in which a separator roller is mounted on a fixed shaft and has a peripheral rubber surface that frictionally engages the peripheral outer surface of the infeed roller or the sheet between the rollers. A tubular coil spring is attached at one end to the separator roller and wrapped around the fixed shaft. When the infeed roller moves in the forward direction, the friction between the outer surfaces of the separator and infeed rollers urges the separator roller forward, thus tending to turn the coil spring on the fixed shaft. This torsion tensions the coil spring. When more than one sheet is passed between the rollers, the infeed roller pushes the top sheet in the forward direction. The separator roller is uncoupled from the infeed roller, as two or more fed sheets between the advancing and separator rollers slip relative to each other. Uncoupling the rollers allows the spring to unwind. The unwinding spring momentarily turns the separator roller backward for about one revolution. An example of this mechanism can be found in Bell and Howell""s Scanner Model Nos. 0101276 and 0101300.
The invention is a sheet feeder for engaging and removing a sheet of paper or other material from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path. The improvements of the present invention address the drawbacks and deficiencies of the prior art in a manner that facilitates high-speed image scanning of individual source documents irrespective of the size or thickness of the specific source document being scanned or processed.
One aspect of the invention is a sheet separator for breaking down multifeeds of two or more overlapping sheets into separate sheets. The separator includes a sheet path, an advancing drive, and a sheet separator assembly including a recoil mechanism and a sheet drag.
The sheet path is the path normally followed by sheets going through the sheet separator. The sheet path is arranged to pass multifeeds of at least two sheets. A multifeed is defined as having first and second opposed outside surfaces. The multifeeds are separated as they travel along the sheet path. The advancing drive is positioned to engage and drive the first surface of the multifeed forward along the sheet path.
The sheet separating assembly includes an advancing drive, a separator roller or other rotatable separator element, a recoil mechanism (also known as a sheet return mechanism), a drag, and optionally a roller sleeve. The advancing drive engages and drives the first surface of the multifeed in the feed direction along the sheet path.
The separator element is rotatable by the second surface of the multifeed in the feed direction and also is rotatable in the counterfeed direction. The recoil mechanism accepts rotational energy, as by winding up or otherwise flexing a spring, by lifting a weight, by compressing an enclosed charge of gas, or by some other mechanism, when the separator element is rotated in the feed direction by advancement of the second surface of the multifeed. The accumulated rotational energy biases the separator element to rotate in the counterfeed direction.
The recoil mechanism releases the accumulated energy and rapidly returns the lower sheet or sheets of a multifeed in the counterfeed direction, thus positively retracting at least the bottom sheet of the multifeed, when the multifeed gets between the drive roller and the separator assembly. The drag resists rotation of the rotatable element in the feed direction, thus retarding the progress of at least the bottom sheet of any multifeed.
The roller sleeve has an outer, generally cylindrical surface positioned to frictionally engage and be rotated by the second surface of the multifeed. The roller sleeve has an inner, generally cylindrical surface coupled to the rotatable element. Rotation of the rotatable element is retarded by the drag and the sheet return mechanism, as described above. The net result is that the sheet separator assembly retards the forward progress of the second surface of the multifeed and positively drives the bottom sheet in the reverse direction, while allowing the top sheet defining the first surface of the multifeed to be driven forward without interruption.
The roller sleeve can be axially slidable on the rotatable element for ready installation on and removal from the rotatable element, if desired.
Another embodiment of the invention is a paper drive for engaging and removing a sheet having an exposed surface from one end of a stack of sheets and feeding the engaged sheet edgewise along a feed path. The paper drive includes at least one roller and a freewheeling mechanism.
The roller has a rotation axis. The roller is positioned to drive the outside sheet of a stack forward into the sheet path. The roller is driven in the direction driving a sheet forward into the sheet path. The drive engages the roller through a freewheeling clutch or similar arrangement.
The freewheeling mechanism independently allows the corresponding roller free rotation in the forward direction when the sheet is moving forward faster than the peripheral speed of the roller. The sheet can be moved faster than the roller by later elements along the sheet path, such as a sheet separator or traction rollers. Thus, when the forward end of the sheet reaches a later element operated at a faster speed, the skimmer drive will not resist acceleration of the sheet by the later element.